My 365 That Isn't

[George C.]

Re: My 365 That Isn't

Clem,
That is true, I think I am past the point of thinking I am going to get out of this cheaply. That is unless I just replace the cam and put it back together again. Thank you for the responses on the Camshaft, I am searching all the forums trying to see if I can find any specs on it.

George

you will need to rebalance the rotating assy if you change piston unless they are the same weight

[George C.]

Re: My 365 That Isn't

Thanks Michael, that is what I am thinking too.
George

That sounds like the best idea so far.

[Joe C.]

Re: My 365 That Isn't

Hi Guys,
I have removed the camshaft and the exhaust lobe on # 8 is hte only one showing destruction. Now I need to identify what the camshaft is, I have searched the board and hte archives, and the Corvette Forum and didn't find this number anywhere.
The number on the shaft is C1M302-R. The logo looks like an arrow in a circle.

I am almost afraid to ask, but does anyone have an idea what this cam is?

Thank you,
George

Here you go:

http://www.jalopyjournal.com/forum/showthread.php?p=8201074

[George C.]

Re: My 365 That Isn't

Joe,
Amazing find, thank you. If I have it right it must have 302 degrees duration, and the R variation says White Box, not sure what that means. I have joined that forum, and am posting the question.

Thank you again,
George

[Joe C.]

Re: My 365 That Isn't

FYI: Federal Mogul Speed Pro says that their blueprinted version of the 30-30 has 310 degrees duration @ J604d (it's misprinted as "295" in another), so your removed cam sounds like it's possibly a 30-30 clone. If it has .323/.323 lobe lift, then it is. With a whopping 56 degrees delta on a meager lobe lift of .323" between durations at J604d and .050", it shows how agonizingly slow the 30-30's ramps are. As an example, a modern solid roller, such as the one I installed in my engine, has a delta of 38 degrees with lobe lift of .395".

[George C.]

Re: My 365 That Isn't

Joe,
The 1965 GM documentation I have, the AMA specs, claim a duration of 346 degrees for the "30-30" cam. Is that correct, and if so quite a difference from the one that is in it which seems to be only 302. The lift did measure out to be .323.
I agree that the removed cam could be a 30-30 clone, somewhere on that HAMB site you told me about it said those cams were around $30.00, I am guessing that was much cheaper than buying one from your Chevy Parts counter. Can you define J604d, I don't understand that term.

Thank you,
George

FYI: Federal Mogul Speed Pro says that their blueprinted version of the 30-30 has 310 degrees duration @ J604d (it's misprinted as "295" in another), so your removed cam sounds like it's possibly a 30-30 clone. If it has .323/.323 lobe lift, then it is. With a whopping 56 degrees delta on a meager lobe lift of .323" between durations at J604d and .050", it shows how agonizingly slow the 30-30's ramps are. As an example, a modern solid roller, such as the one I installed in my engine, has a delta of 38 degrees with lobe lift of .395".

[Joe C.]

Re: My 365 That Isn't

Joe,
The 1965 GM documentation I have, the AMA specs, claim a duration of 346 degrees for the "30-30" cam. Is that correct, and if so quite a difference from the one that is in it which seems to be only 302. The lift did measure out to be .323.
I agree that the removed cam could be a 30-30 clone, somewhere on that HAMB site you told me about it said those cams were around $30.00, I am guessing that was much cheaper than buying one from your Chevy Parts counter. Can you define J604d, I don't understand that term.

Thank you,
George

George,

At what valve lift point is the AMA spec of 346 degrees measured? There are more than a few points at which duration is measured; the one which is always used is the duration at 0.050" valve lift, which is 254/254 for the 3849346 cam. The durations for at least 2 valve lift points are needed in order to "define" the cam's dynamics. The other points that are commonly used, in addition to 0.050" valve lift, and depending on manufacturer are: 0.200" valve lift, 0.015" valve lift, and "seat-to-seat", AKA "advertised", AKA SAE J604d duration. With the exception of 0.200" valve lift, these points are used to define the valve lift where flow effectively becomes zero. Competition Cams uses 0.015" valve lift as the effective minimum point below which flow across the seat ceases, and so, as their version of "advertised" duration. SAE J604d should be the industry standard, and I suppose that it never has become standardized as a means of muddying the waters, confusing the consumer and thus, adding grist to the marketing mill. SAE J604d duration is the duration between opening and closing points when the valve is at 0.006" lift. As you can see, it becomes more difficult to define the lift point at which the valve flow becomes zero for a cam with very gentle dynamics because the valve is moving so slowly. It's much easier to define "the point at which flow effectively drops to zero" for a cam with fast ramps because the valve quickly reaches and passes the target lift.

The cam that you need, if you go ahead with the 30-30 is Federal Mogul Speed Pro CS118R, which can be bought at an excellent price, here:

http://www.northernautoparts.com/ProductModelDetail.cfm?InventoryId=35040

Joe

[Michael H.]

Re: My 365 That Isn't

George,

At what valve lift point is the AMA spec of 346 degrees measured?

Joe

Joe,

GM used .020" as a checking clearance for the 3849346 cam. (and most other mech lifter cams of the era)

[Joe C.]

Re: My 365 That Isn't

At what valve lift point is the AMA spec of 346 degrees measured?

Joe,

GM used .020" as a checking clearance for the 3849346 cam. (and most other mech lifter cams of the era)

Michael,

I don't think that you're saying that the 346 degree AMA spec is @ 0.020" valve lift, because if you are, then that's incorrect. I have the measured cam degree versus lift data for the 3849346 cam, and IIRC, the J604d (which is .006" valve lift) squares with one of Sealed Power's "advertised" durations published as 310/310. If that cam has 346 duration @ 0.020" valve lift, then it would have an absurd J604d ("advertised/"seat-to-seat") duration in the neighborhood of 360 degrees!

The reason I included 0.200" as a possible duration point is because I've seen it on a few cam cards, and it also appears in Engine Analyzer Pro's camshaft configuration screen. If it's not visible due to the size limitations placed on photos appearing here, zoom in with your browser and look at the drop down menu on the right side of this screenshot:

[George C.]

Re: My 365 That Isn't

Joe,
Hi, the AMA specs I got from GM list the duration as 346 degrees 13' for both intake and exhaust, and the lift @ zero lash at .4851. The 1965 supplement to the Corvette Shop manual does not list the duration, only the lift of .4850 at the valve stem.
George

[Duke W.]

Re: My 365 That Isn't

The "346 degrees" is essentially from the end of the .017" high opening clearance ramp to the beginning of the closing clearance ramp, which also starts .017" above the base circle, although from my analysis of the engineering data, which consists of lobe lift to five decimal places every cam degree I come up with a slighly different number.

This was GM's way of measuring duration back then, and it does not conform to any current "standards", so it cannot be compared to any other cam specs.

The actual .050" lift duration, ABOVE THE TOP OF THE CLEARANCE RAMP, which would be .067" above the base circle is 239 degrees, and this number you can roughly compare to hydraulic lifter cams specified .050" duration.

If you do a little research you will find that 230 degree is generally considered a maximum for sensible street application on a short stroke small block.

Duke

[Joe C.]

Re: My 365 That Isn't

In post #86, 239 degrees is mentioned as the true duration of the 30-30 cam @ 0.050" valve lift. 239 degrees is the corrected duration due to the fact that Chevy stamped steel rocker arms are not truly1.5:1, and at the lash point the ratio is actually 1.37:1.

That's a true statement, but I wanted to point it out, so as to eliminate any possible confusion for you. The published duration at 0.050" valve lift, assuming a theoretical 1.5:1 rocker arm ratio, is 254/254.

[Duke W.]

Re: My 365 That Isn't

254 @ .050" is the duration of the 30-30 cam including the clearance ramps, but the valves don't move until the clearance is taken up, which is why you cannot directly compare the .050" duration of any mechnanical lifter cam to a hydraulic lifter cam.The 30-30 cam has .017" high cleance ramps, so the .067" duration, which can be determined from the engineering lobe data is comparable to the .050" duration of a hydraulic lifter cam. I don't know how I can be more clear.If lash is set at 1.37 x .017" = .023" then you get the full duration. Loser lash will shorter duration by a few degrees, but it increases valvetrain shock load as the valve is jerked off the seat and slammed back down at greater the the clearance ramp velocity.Duke

[George C.]

Re: My 365 That Isn't

Joe, Duke,
Thank you both, that helps us novice to understand why there are so many different specs on the 30-30 cam duration.
George

[John M.]

Re: My 365 That Isn't

I used Joe and Dukes recommended clearances on both a hydraulic lifter 327-300 and aSHP 427-435 and have only one, sort of, negative comment. The 427-435 valve train is very quiet, many people would say it has hydraulic lifters.
For the 30-30 cam, GM made thousands of Corvettes with these, presumably set at 0.030", so although 0.023" might be ideal, how bad can 0.030" really be?